Liquid crystal display devices are display devices which control alignment of liquid crystal molecules by using an electric field formed between electrodes, thereby controlling ON and OFF of liquid crystal display. According to common LCD devices, electrodes for applying a voltage to LC molecules are pattern-formed in a specific shape and size, and the electrodes as a pixel unit drive and control the LC molecules. Thus the LCD devices can provide high-definition display.
LCD devices are classified into transmissive LCD devices and reflective LCD devices based on the kind of display light. The transmissive LCD devices include a light source such as a backlight and use light from the light source as display light. The reflective LCD devices include a reflector and use ambient light reflected by the reflector as display light. In recent years, transflective LCD devices which can provide both transmissive display and reflective display have attracted attention. The transflective LCD devices can provide mainly transmissive display under indoor environments and mainly reflective display under outdoor environments. So the transflective LCD devices can provide high quality display under any environments, both indoor and outdoor environments. The transflective LCD devices are installed in various mobile equipment, such as a cellular phone, a PDA, and a digital camera.
VA (vertical alignment) LCD devices are commonly used as one of the LCD devices. In the VA LCD devices, display is controlled by aligning LC molecules vertically to substrate surfaces in a voltage-off state and aligning the LC molecules in a direction parallel to the substrate surfaces in a voltage-on state. The VA LCD devices typically show a high contrast ratio, which shows luminance of white state and black state, and also shows a wide viewing angle by aligning LC molecules in various directions in one pixel. MVA (multi-domain vertical alignment) LCD devices and CPA (continuous pinwheel alignment) LCD devices are known as one of the VA LCD devices allowing alignment division more effective in wide viewing angle. In the MVA LCD devices, a linear-shaped dielectric protrusion is formed on a substrate surface facing a liquid crystal layer, or a slit is provided for a pixel electrode. In the CPA LCD devices, dielectric protrusions are formed in a dotted pattern on a substrate surface facing a liquid crystal layer of a pixel electrode, and distortion of an electric field created between the dielectric protrusions and edges is utilized.
When alignment control structures, such as the protrusion and the slit, are arranged, LC molecules around the structures are in an alignment state different from that of LC molecules in other regions. This might cause light leakage when a voltage is applied, leading to a reduction in contrast. In order to improve the contrast by suppressing such light leakage, Patent Document 1 discloses, for example, a CPA LCD device that permits high contrast display by shielding a region overlapping with the alignment control structures as viewed in plane.
In VA LCD devices, transmittance in oblique directions less depends on a driving voltage, which results in deterioration of color reproducibility. In order to improve display characteristics of the VA LCD devices, a control capacitance electrode is provided to form a plurality of regions different in capacitance in a pixel. However, such a control capacitance electrode is made of a light blocking metal film, and therefore an aperture ratio of the pixel is decreased and luminance is reduced. In order to improve the aperture ratio of a pixel, Patent Document 2 discloses that, for example, part of a control capacitance electrode is arranged to overlap with a region where a linear-shaped protrusion is formed and light transmittance is lower than that of other regions.
The LCD devices are now being rapidly developed. Simple methods for a further improvement in display qualities are strongly needed.
[Patent Document 1]
Japanese Kokai Publication No. 2006-58734
[Patent Document 2]
Japanese Kokai Publication No. 2006-201356